This invention relates to a cleaning machine, and in particular, a machine for cleaning annular discs suitable for use in Winchester or other disc drive memory systems.
A commonly-used memory system, known as a Winchester disc drive system, uses thin, annular metal discs coated with a memory receiving coating. It is typical that such discs are made of aluminum. The aluminum disc must be clean and free from dirt, oil, and other contaminants in order to properly accept a memory surface coating. Other discs of rigid or flexible (floppy) material also must be cleaned before they are coated.
In U.S. Pat. No. 3,479,222, there is described a cleaning apparatus for cleaning an annular metal memory disc previously coated with a memory layer. That patent describes a machine that uses rollers or wheels spaced about the periphery of the disc. The wheels orient and retain the disc and also turn the disc while cleaning fluid is applied to it. That patent does not indicate whether or not such a method and apparatus would be suitable for cleaning discs before they are coated with a memory coating.
It is also known that devices such as photomasks or semiconductor wafers can be cleaned and dried by mounting them on a vacuum chuck, spraying suitable cleansing fluid, such as dionized water, onto the device and spinning the device until it is dry. For examples of such apparatus, see U.S. Pat. Nos. 4,161,256; 4,064,885; and 4,027,686. Such apparatus would not, however, readily accept an annular disc member. This is so since such apparatus frequently use a spindle having a vacuum chuck disposed underneath the wafer or the photomask for holding the planar surface of the item on the spindle during operation. Since an annular disc has a central opening, a vacuum chuck would not be appropriate. Moreover, such apparatus only cleans one surface of the item at a time and it would be desirable to clean simultaneously both surfaces of the annular disc.
It has also been proposed by others to provide a spindle that has vacuum operated jaws which extend and grip the inside ring of the annular disc so that the disc can then be rotated. Such devices unfortunately have encountered problems. The mechanism needed to actuate gripping jaws through a central spindle is mechanically complex. Moreover, such devices have not been able to completely clean the discs and spin them dry since some water remains in crevices of the jaw mechanism.
A disc blank can be completely cleaned within 30 seconds if each side is subjected to a stream of dionized water at 2,500 to 5,000 psi while the disc was rotated between 2,500 to 5,000 revolutions per minute. In such a machine it would be desirable to minimize hand contact with the disc. Accordingly, it would be desirable to have a machine that self centered and aligned the disc into its proper horizontal plane of rotation. Since a high-pressure stream of water would be directed against both sides of the disc, some fail-safe means would be desired to hold the disc on the spindle in the event that the upper high pressure spray became clogged or otherwise inoperable. The latter condition would leave the disc under the influence of the lower spray that would tend to force the disc off the spindle. Should a disc rotating at such high speeds leave the spindle, damage to the cleaning machine could be considerable. In addition, any people in the immediate area could be injured if a rigid metal disc left the spindle. Of course, in any such cleaning machine, there must be some means for imparting the desired rotation to the disc.